Method and device for polarizing a DBD electrode

Abstract

The invention relates to a device for treating the surface of a substrate by means of dielectric barrier discharge for generating a filamentary plasma, including a reaction chamber comprising a mixture having a composition such that, when in contact with the plasma, the mixture decomposes and generates species capable of deposition in the form of a layer mostly or totally on the substrate, wherein at least two electrodes area provided in said chamber, with one electrode being subjected to a high AC voltage, and are arranged on either side of the substrate, at least one dielectric barrier (DBD) arranged between said at least two electrodes, and a THT/HF transformer comprising a secondary circuit, in which a direct current (DC) power source is provided in series in the secondary circuit such that the chemical species generated in the plasma in the form of electrically positive or negative ions are selectively attracted by the target substrate inserted in the reaction chamber and arranged between said at least two electrodes, and repelled by electrodes having a corresponding charge.

The invention claimed is: 
     
       1. A method for depositing a film on an inorganic substrate, the method comprising:
 providing a power supply stabilized in amplitude and in frequency, the power supply comprising a transformer having a secondary circuit comprising secondary terminals connected to two plasma-generating electrodes; 
 introducing or passing a substrate in a process chamber with said two plasma-generating electrodes on either side of the substrate and with a dielectric barrier between the two plasma-generating electrodes such that the substrate is passed in between the two plasma-generating electrodes connected to the secondary terminals; 
 coupling power from the transformer via said secondary terminals to the two plasma-generating electrodes inside the process chamber; 
 generating, in the secondary circuit of the transformer, a stabilized electrical AC voltage, and thereby generating a filamentary plasma in the process chamber in between the two plasma-generating electrodes, the plasma comprising electrons, neutral species, positive and negative ions, species in a stable and an excited state, or a combination thereof; 
 supplying DC current in series with the transformer by a DC supply, thereby generating a DC voltage superimposed on the AC voltage, and increasing a polarity of the substrate and decreasing a polarity of an electrode, or vice versa, depending on a value of the AC voltage; 
 introducing into the process chamber a mixture with a composition such that, upon contact with the plasma, the mixture decomposes and generates species able to be deposited as a film onto the substrate; and 
 maintaining the substrate in the chamber for a time sufficient to obtain a layer with a desired thickness on a face of the substrate. 
 
     
     
       2. The method of  claim 1 , further comprising:
 adjusting a value of the DC voltage such that the AC voltage does not reach a plasma initiation value in a polarity direction. 
 
     
     
       3. The method of  claim 1 , further comprising inverting a polarity of the DC voltage with respect to the substrate. 
     
     
       4. The method of  claim 1 ,
 wherein the DC voltage is between 20 and 100 kV, thereby reducing unwanted deposits by at least 15%. 
 
     
     
       5. The method of  claim 4 , wherein the DC voltage is between 20 and 80 kV. 
     
     
       6. The method of  claim 4 ,
 wherein the DC voltage is between 20 and 60 kV. 
 
     
     
       7. The method of  claim 4 ,
 wherein the DC voltage is between 20 and 100 kV, thereby reducing unwanted deposits by at least 35%. 
 
     
     
       8. The method of  claim 1 ,
 wherein the mixture deposits a film mostly or totally on the substrate. 
 
     
     
       9. The method of  claim 1 , wherein the transformer comprises a high voltage (VHV) transformer capable of a voltage between 15.1 and 100 kV. 
     
     
       10. The method of  claim 1 , wherein said supplying DC current in series comprises superimposing for the DC voltage a voltage between 15.1 kV and 100 kV. 
     
     
       11. The method of  claim 1 , wherein said maintaining the substrate in the chamber comprises maintaining the chamber in a pressure range close to atmospheric pressure. 
     
     
       12. The method of  claim 1 , wherein supplying DC current comprises supplying DC current in series with a cold side of the transformer. 
     
     
       13. The method of  claim 1 , wherein supplying DC current comprises supplying DC current from a DC source having floating poles permitting a positive or negative polarization to be supplied to one of the two electrodes. 
     
     
       14. The method of  claim 1 , wherein supplying the DC current in series with the transformer comprises supplying a DC current by a DC supply disposed between ground and an inductor connecting to a powered electrode of the two electrodes. 
     
     
       15. The method of  claim 1 , further comprising using the DC voltage superimposed on the AC voltage to reduce or suppress deposition of the species on at least one of the two electrodes connected to the secondary terminals. 
     
     
       16. A method for depositing a film, comprising:
 coupling power from a transformer via secondary terminals of the transformer to two plasma-generating electrodes disposed inside the process chamber; 
 introducing or passing a substrate between the two plasma-generating electrodes disposed inside a process chamber and having a dielectric barrier between the two plasma-generating electrodes connected to the secondary terminals of the transformer; 
 generating, in a secondary circuit of the transformer, an electrical AC voltage; 
 generating a filamentary plasma in the process chamber, between the two plasma-generating electrodes; 
 supplying DC current in series with the transformer to at least one of the two electrodes by a DC supply; 
 introducing into the process chamber a mixture with a composition such that, upon contact with the plasma, the mixture decomposes and generates species to be deposited as a film onto the substrate; and 
 maintaining the substrate in the chamber to obtain a layer on the substrate. 
 
     
     
       17. The method of  claim 16 , wherein the transformer comprises a high voltage (VHV) transformer capable of a voltage between 20 and 100 kV. 
     
     
       18. The method of  claim 16 , wherein said maintaining the substrate in the chamber comprises maintaining the chamber in a pressure range close to atmospheric pressure. 
     
     
       19. The method of  claim 16 , wherein supplying DC current comprises supplying DC current in series with a cold side of the transformer. 
     
     
       20. The method of  claim 16 , wherein supplying DC current comprises supplying DC current from a DC source having floating poles permitting a positive or negative polarization to be supplied to one of the two electrodes. 
     
     
       21. The method of  claim 16 , wherein supplying the DC current in series with the transformer comprises supplying a DC current by a DC supply disposed between ground and an inductor connecting to a powered electrode of the two electrodes. 
     
     
       22. The method of  claim 16 , further comprising using the DC voltage superimposed on the AC voltage to reduce or suppress deposition of the species on at least one of the two electrodes connected to the secondary terminals.